The invention relates to an apparatus for the fibre-sorting or fibre-selection of a fibre bundle comprising textile fibres, especially for combing.
In certain known apparatus, fibre bundles are supplied by means of a supply device to a fibre-sorting device, especially to a combing device, in which clamping devices are provided, which clamp the fibre bundle at a distance from its free end, and mechanical means are present which generate a combing action from the clamping site to the free end of the fibre bundle, a circulating means for removing the combed fibre material being present, which is provided on its periphery with air-permeable openings and at least part of the inner space of which is connected to a source of reduced pressure.
In practice, combing machines are used to free cotton fibres or woollen fibres of natural impurities contained therein and to parallelise the fibres of the fibre sliver. For that purpose, a previously prepared fibre bundle is clamped between the jaws of the nipper arrangement so that a certain sub-length of the fibres, known as the “fibre tuft”, projects at the front of the jaws. By means of the combing segments of the rotating combing roller, which segments are filled with needle clothing or toothed clothing, this fibre tuft is combed and thus cleaned. The take-off device usually consists of two counter-rotating rollers, which grip the combed fibre tuft and carry it onwards. The known cotton-combing process is a discontinuous process. During a nipping operation, all assemblies and their drive means and gears are accelerated, decelerated and in some cases reversed again. High nip rates result in high acceleration. Particularly as a result of the kinematics of the nippers, the gear for the nipper movement and the gear for the pilgrim-step movement of the detaching rollers, high acceleration forces come into effect. The forces and stresses that arise increase as the nip rates increase. The known flat combing machine has reached a performance limit with its nip rates, which prevents productivity from being increased. Furthermore, the discontinuous mode of operation causes vibration in the entire machine, which generates dynamic alternating stresses.
WO 2006/012758 A discloses a combing machine, in which a fibre bundle drawn off by two draw-off rollers is supplied discontinuously to a downstream perforated drum under the influence of an air current and is added to the fibre web already formed (piecing). The leading end of the fibre web conveyed by the draw-off rollers is pushed in this process towards the perforated drum. The perforated drum also performs a clockwise rotation. Inside the perforated drum there is arranged a rotatable cylinder with two openings, which, in conjunction with the rotary movement of the cylinder, ensure that the leading end of the fibre bundle is deflected in the direction of rotation of the perforated drum, whilst the trailing end of the fibre bundle, after the draw-off rollers have released it, is deposited on the perforated drum. The disadvantage is the high expenditure on equipment. In particular it is a disadvantage that a high production is not possible. The rotational speed of the draw-off rollers that convey the fibre bundle is adapted to the upstream slow combing process and is limited by this. A further drawback is that each fibre bundle is clamped and conveyed by the draw-off roller pair. The clamping point changes constantly owing to the rotation of the draw-off rollers, i.e. there is a constant relative movement between the rollers effecting clamping and the fibre bundle. All the fibre bundles have to pass in succession through a draw-off roller pair, which represents a further considerable limitation of the production speed.